In the past two decades, the use of pressure-treated lumber such as WOLMANIZED.RTM. lumber has increased remarkably due to its increased resistance to rot. While the underground portions of such WOLMANIZED timbers show greatly increased rot resistance, particularly when encased in cement, problems still occur at grade-level, where the combination of water, sunlight, and microorganisms encourages rot.
Moreover, treated lumber is generally of a different color, and weathers differently from other forms of lumber frequently used for decorative fencing. Consumers frequently dictate that fencing materials be of more attractive natural colored woods such as redwood, cedar, and cypress. However, these untreated timbers are more prone to grade-level rot, which is the frequent source of failure in such fencing materials.
Wooden fence posts, even those of the pressure-treated variety, may be coated with a variety of paints and varnishes to increase their resistance to rot. However, in addition to being only marginally effective, application of these treatments is both time and labor intensive, and moreover, most such coatings do not weather well, resulting in the necessity for frequent repainting.
The effect of grade-level rot is particularly important, as illustrated by U.S. Pat. No. 4,989,834, where upwardly extending wooden fence elements are actually maintained above ground level by specially designed supports, thus preventing ground rot in these upwardly extending elements.
In U.S. Pat. No. 3,562,403 is disclosed resin-coated wooden poles for mounting light standards, prepared by machining a groove into the wooden pole to encourage thorough penetration of rot-preventing chemicals, following which a shielded electrical conduit is placed in one of the grooves, the surface filled with putty or other substance, and the entire pole spray-coated with a mixture of chopped glass fibers and catalyzed polyester resin. The process of U.S. Pat. No. 3,562,403 is an expensive process, and one which is not amenable to in-the-field production. Moreover, the pole thus treated does not have the appearance of a wooden product, but of a plastic pole.
In U.S. Pat. No. 4,516,756 is disclosed a molded plastic sheath which is inserted over the top of an existing fence post to prevent above-ground weathering, and eliminate the step of painting a fence post, for example when installing picket fences. However, such plastic sheathing is ineffectual for eliminating ground level rot, and gives the exposed post a plastic rather than natural wood appearance.